1. Field of the Invention
This invention relates to a thin reinforced nonwoven fabric having ridges and grooves made from a compressed web of crimped fiber and a reinforcing scrim. The fabric bulks when exposed to heat or flame and is useful as a component for fire blocking mattresses, upholstery, and the like, especially those that are substantially made from foam. This invention further relates to a fire-blocked article incorporating this fabric.
2. Description of Related Art
The State of California has led the drive to regulate and reduce the flammability of mattresses and mattress sets in an attempt to reduce the number of lives lost in household, hotel, and institutional fires. In particular, the Bureau of Home Furnishings and Thermal Insulation of the Department of Consumer Affairs of the State of California issued Technical Bulletin 603 “Requirements and Test Procedure for Resistance of a Residential Mattress/Box Spring Set to a Large Open-Flame” to quantify the flammability performance of mattress sets. In many cases, mattress makers want to include a layer of fire blocking, however, they do not want that additional layer to detract from the existing aesthetics of their mattresses.
Strong thin fabrics, such as a combination of staple fibers and a thin reinforcing scrim fabric, could be desired in many instances because they are durable and also are not likely to be objectionable. Various methods are known in the art for combining staple fibers and scrim fabrics that lock the staple fibers in place. One such process is hydro-entangling, also known in various publications as hydrolacing, spunlacing, and water-jet treatments, where high pressure water jets impact the staple fibers and drive them into the scrim, consolidating the fiber and scrim together. Another process known in the art for combining staple fibers and scrim fabrics is by needlepunching. In this process, barbed needles grab the staple fibers and drive them into the scrim, or into the internal fiber batting, locking together the structure. Nonwoven sheets made by these processes mechanically and strongly entangle the staple fibers either with themselves or with the scrim or both, limiting the ability of the fabric to bulk when heated or exposed to flame.
Still another process known in the art for combining staple fibers and scrim fabric is by adhesive lamination or the addition of binders. In this process, a binder or adhesive is used to either adhere or bind layers or individual fibers together. For example, U.S. Pat. Nos. 6,579,396 and 6,383,623 to Erb disclose a very low-density insulating material having non-thermoplastic fibers that are bound by a flammable thermoplastic binder. European Patent EP 622 332 to Yamaguchi et al. discloses a heat resistant and flame-retardant cushioning structure comprising a matrix fiber of a bulky nonwoven web of crimped non-elastic staple fiber, a crimped flame-retardant fiber exhibiting residual weight of at least 35% as tested by a glowing test method, and a thermoplastic elastic fiber; with at least some of the intersecting points between the matrix fiber and the flame-retardant fiber with thermoplastic fiber being fusion bonded. The Erb and Yamaguchi patents both use the binder to maintain the loft or thickness of these thick fabrics; that is, the nonwoven remains in a lofted or bulked form so that it will have resiliency.
The process of incorporating a fabric into a mattress can be made more difficult if the mattress is a foam mattress. Typically the fabric to cover the mattress is sewn into a sleeve or pocket-type structure; the foam mattress is then mechanically compressed and the sleeve structure slid over mattress. The mechanical compression is released and the foam mattress then fills the covering sleeve. This process requires that the sleeve material have enough elongation or give so that it does not tear while being installed on such a mattress or when the foam mattress fully extends to its original shape.
U.S. Patent Application Publication US 2003/0213546 of Hartgrove discloses a durable, extensible nonwoven fabric that is suitable for mattress pad covers wherein the skirt of the mattress pad cover must exhibit extensibility so as to expand over the thickness of the mattress on which the cover is fitted. This fabric, like the hydroentangled nonwoven it is made from, has very limited ability to bulk when heated or exposed to flame due to the mechanical entanglement of the fibers.
What is needed therefore, is a reinforced nonwoven fabric that can elongate to facilitate installation on a foam mattress without tearing and is lightweight and thin during normal use but then bulks when subjected to high heat or flame.